1. Field of the Invention
This invention relates to a stator, and more particularly to a stator used in an ultrasonic motor.
2. Description of the Related Art
Referring to FIGS. 1 and 2, Taiwanese utility model patent No. M286995 discloses an ultrasonic motor that includes a motor base 11, an elliptical stator 12, a support prepressing mechanism 13, and a target object 14. The elliptical stator 12 includes an elliptical elastic body 121, two piezoelectric actuators 122 disposed inside the elliptical elastic body 121, and a mounting post 123 disposed between the piezoelectric actuators 122. Upon application of driving voltages, the piezoelectric actuators 122 are extended and contracted to allow for vibration of a driving protrusion of the elliptical body 121 in an elliptical motion to drive movement of the target object 14.
The aforesaid ultrasonic motor suffers from the following disadvantages:
1. Low strength: The elliptical elastic body 121 of the stator 12 is connected to a supporting seat 131 of the support prepressing mechanism 13 by the mounting post 123. As such, the elliptical elastic body 121 is spaced apart from the supporting seat 131, thereby resulting in a reduction in the strength of the elliptical elastic body 121. Consequently, the elliptical elastic body 121 is easily deformed, so that the target object 14 cannot be driven accurately.2. Complex structure: The elastic body 121 is mounted to the bottom base 11 by the supporting seat 131. Such a complex structure results in an increase in the manufacturing costs of the ultrasonic motor.3. Poor precision: Since the ultrasonic motor has a complex structure, errors occur easily during assembly of the ultrasonic motor. That is, the precision of the ultrasonic motor is reduced. Moreover, since the elastic body 121 has a low strength, the precision of the ultrasonic motor is further reduced.